1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, more particularly, to an image forming apparatus in which stress on a toner and power consumption are reduced.
2. Description of the Related Art
Referring to FIG. 1, a conventional electrophotographic image forming apparatus 1 includes a feeding unit 10, a transport unit 20, developing units 30C, 30M, 30Y and 30K which each store predetermined colors of toners, a plurality of transfer rollers 40, a light scanning unit (LSU) 43, a fixing unit 50 and a discharging unit 60. A printing medium which is stacked on a knockup plate 12 elastically supported by a spring 11 is picked up by a pickup roller 13 and its leading edge is aligned by a registration roller 14. The aligned printing medium is transported by a transport belt 25 of the transport unit 20 to the developing units 30, and a color toner image is formed on the printing medium via the developing units 30C, 30M, 30Y and 30K. The color toner image formed on the printing medium is fixed with heat and pressure by a heat roller 53 and a press roller 55. The printing medium which is completed in printing via the fixing unit 50 is discharged by a discharging roller 63 to the outside.
However, the conventional image forming apparatus 1 uses eight motors, four of which are to drive the fixing unit 50, a transport belt driving roller 27, the discharging roller 63 and the pickup roller 13 respectively, and the other four to drive the respective developing units 30C, 30M, 30Y and 30K. Further, the driving motors (not illustrated) for the developing units 30C, 30M, 30Y and 30K drive photosensitive drums 35C, 35M, 35Y and 35K, developing rollers 33C, 33M, 33Y and 33K, and agitators (not illustrated), respectively, and transmission of power from the driving motors to the developing rollers 33C, 33M, 33Y and 33K and the agitators is controlled by a solenoid.
Thus, using eight motors, the conventional image forming apparatus 1 has a complicated structure to transmit power, consumes more electric power, and increases manufacturing cost and a driving noise. Also, when the image forming apparatus 1 prints black and white images, though power in the developing rollers and the agitators is controlled by the solenoid, the photosensitive drums are still being driven. Accordingly, stress on the toner may increase.